1. Field of the Invention
The present invention relates generally to automatic code symbol reading (i.e. recognition) systems, and more particularly to an automatic code symbol reading device having a control system which permits multiple modes of fully automated operation while conserving power and providing versatility in its method of use.
2. Brief Description of the Prior Art
Hitherto, a number of techniques have been proposed for reading bar code symbols using hand-held devices. Despite variety amongst prior art bar code symbol reading devices, the various techniques incorporated into prior art devices can be classified into two principally distinct classes, namely, manually operated or triggered bar code symbol reading, and automatic bar code symbol reading.
Representative of prior art manually operated bar code symbol reading devices are U.S. Pat. No. 4,387,297 to Swartz, et al., U.S. Pat. No. 4,575,625 to Knowles, and U.S. Pat. No. 4,845,349 to Cherry. While such prior art devices are capable of successful bar code symbol reading, they nevertheless suffer from several significant shortcomings and drawbacks. In particular, the user is required to manually pull a trigger or push a button each time scanning and decoding is to be cyclically initiated and terminated. The requirement is most fatiguing on the user when large numbers of bar code symbols are to be read. Also, in certain symbol reading applications, such as warehouse inventory, pulling the trigger to initiate scanning of bar code symbols may be extremely difficult for the user due to the physical location of the objects bearing the bar code symbols.
An alternative to manually operated a bar code symbol reading devices is use of automatic bar code symbol readers, which incorporate techniques for automatically initiating and terminating scanning and decoding operations. Representative of prior art automatic bar code symbol devices are U.S. Pat. No. 4,639,606 to Boles, et al. and U.S. Pat. No. 4,933,538 to Heiman et al. While capable of automatically initiating scanning of bar code symbols, such prior art devices and incorporated techniques nevertheless also suffer from significant shortcomings and drawbacks.
In particular, U.S. Pat. No. 4,639,606 to Boles, et al. discloses laser emission control circuitry for use in implementing a hand-held triggerless bar code scanner. The laser is operated in a pulsed "find paper" mode until a reflected signal is obtained, indicating the presence of an object (e.g., paper) in the search field. Thereupon, the circuitry is changed to a "search mode" in which the power of the laser is increased to above the safety limits for a period of time, and the return signal is monitored for signal transitions corresponding to the black bars of the code. On detection of the first black bar, the circuitry is changed to an "in-code" (decode) mode as long as successive symbols are received within a given period of time. If the decode mode terminates within a predetermined time interval (e.g., one second after the beginning of the search mode), then the search mode is re-entered, otherwise the decode mode will change to find paper mode.
While the triggerless bar code symbol reader proposed in U.S. Pat. No. 4,639,606 possesses three modes of operation, this prior art bar code symbol reader nevertheless suffers from several significant shortcomings and drawbacks. In particular, this prior art bar code symbol reader requires continuous use of a pulsed laser beam to determine the presence of an object within the scan field, which, in hand-held portable battery power devices, undesirably drains limited power reserves, especially in extended time duration bar code reading applications. Also, this prior art device not knowing whether a bar code symbol is actually present in the scan field, requires commencement of decode processing upon detection of the first black bar. Undesirably, this typically necessitates powering and initializing a programmable device such as a microprocessor, for decoding scan data that may likely contain no bar code symbol at all. Consequently, this characteristic of such prior art bar code symbol reading devices results in further consumption of power.
U.S. Pat. No. 4,933,538 discloses a bar code symbol scanning system, which in the "object sensor mode" the scanner is triggerless and the constantly on laser beam normally emits at a narrow angle and low power. When an indicia pattern indicative of a bar code symbol has been detected, the laser beam will widen, the power of the beam will increase, and the beam will read the entire symbol. While this prior art scanning technique permits detection of bar code symbols within the scan field in order that the power of the laser beam may be automatically increased to a higher level for collecting scan data for use in decoding operations, this prior art system nevertheless suffers from several significant shortcomings and drawbacks as well. In particular, this prior art system requires continuous use of laser emission to determine the presence of both objects and bar code symbols within the scan field, which necessarily results in drain of limited power reserves in portable battery power applications. In addition, the extensive use of a laser beam to perform object and bar code symbol detection functions implicates necessity for laser emission control measures.
In general, prior art automatic bar code symbol reading devices also suffer from other shortcomings and drawbacks. For example, unlike manually operated devices which rely on the user to activate a trigger, once for each bar code to be read, prior art triggerless (i.e., automatic) bar code symbol reading devices lack intelligence capabilities necessary to prevent undesired multiple reading of bar code symbols, particularly when the scanning beam is permitted to dwell on a bar code symbol for extended periods of time.
Further, prior art automatic bar code symbol reading devices have lacked control capabilities which permits diverse modes of programmable system-control operation, while preventing misreads and inadvertent multiple reads and ensuring conservation of power.
Thus, there is a great need in the code symbol reading art for a fully automatic code symbol reading device which overcomes the above shortcomings and drawbacks of prior art devices and techniques.
Accordingly, it is a primary object of the present invention to provide a fully automatic hand-holdable bar code symbol reading device capable of automatically reading bar code symbols in accordance with user-selectable system-control operations.
A further object of the present invention is to provide such an automatic bar code symbol reading device incorporating a control system having a plurality of control centers, each of which can be assigned predetermined control functions that enable operation of particular device components in accordance with a user-selected system-control operation.
A further object of the present invention is to provide such an automatic bar code symbol reading device, in which upon the occurrence of predetermined conditions, one or more of the control centers are capable of overriding certain of the other control centers so that a wide number of system-control operations can be carried out in a power conserving manner, to permit automatic reading of bar code symbols in a variety of diverse applications.
Another object of the present invention is to provide such an automatic bar code symbol reading device, in which the system control architecture readily permits extension of additional system-control operations by formulating and programming functions between a fixed number of control activation signals and enable signals provided as input and output signals respectively, to one or more control centers.
A further object of the present invention is to provide an automatic hand-holdable bar code symbol reading device which is capable of determining the presence of an object without enabling the scanning means of the device.
Another object of the present invention is to provide a hand-holdable bar code symbol reading device which is capable of distinguishing between a bar code symbol and a regular pattern of light and dark areas such as that formed by printed characters, and to only enable decode processing of scan data upon the detection of a bar code symbol in the scan field of the device. Consequently, the device is capable of disregarding all text within the scan field, and enabling the symbol decoder only by an actual bar code symbol.
An even further object of the present invention is to provide an automatic bar code symbol reading device which prevents multiple reading of bar code symbols due to dwelling of scanning beam upon a bar code symbol for an extended period of time.
Yet a further object of the present invention is to provide an improved method of automatically reading bar code symbols.
These and further objects of the present invention will become apparent hereinafter and in the claims.